Why do we need water?

Everybody knows that they need to drink water, especially while exercising or competing, but few understand the science behind exactly why.

Water makes up most of the human body, including 80 percent of our blood, 90 percent of our lungs and 70 percent of our brain. All told, about 60 percent of our bodies are made out of water. But what is the active role of water in our bodies? Why are doctors, trainers and fitness magazines always telling us to drink more water? How much do we really need?

What it Does

Water is necessary to our every bodily system. In addition to being a major building block of organs and tissues, it keeps things running smoothly.

The liver and kidneys, which both produce large amounts of waste during their filtration work, rely on water to carry that waste away.

Water lubricates your joints, as well as moisturizes your inner ear, eyes, nose and throat.

Because of its major role in the composition of blood, water is responsible for the transportation of nutrients to your cells and muscles. Blood also carries waste away from these areas.

Your internal temperature is also regulated by water. Even when you aren’t aware of it, your body is producing small amounts of sweat through the glands on your skin to control your temperature. This sweat is comprised mostly of water.

Where Does it All Go?

Even when you aren’t working out, or moving much at all, your body loses a surprising amount of water. The average person exhales one cup’s worth of water vapors every day, plus another six cups lost to urine and bowel movements.

Then, of course, there is the water you sweat out. The average person excretes about four cups of water per hour during high-intensity exercise, according to researchers at the University of New Mexico. This number could change, however, based on fitness level, health conditions, age and surrounding weather.

How Much is Enough?

If you lose, on average, seven cups of water per day before you even start to sweat, you need to replenish at least that much. Remember the old adage to drink at least eight cups of water a day? It’s solid advice.

Depending on your diet, this could even give you slightly more water than you need. Most people receive about 20 percent of their daily hydration needs from their food, according to the Mayo Clinic. But a little bit of extra water won’t do any harm.

If you’re exercising, you will need to compensate for the water lost from sweat. For a typical workout, lasting about 30 minutes, about two cups of extra water should be enough. During longer, more intense workouts, you’ll need to adjust your water intake and possibly use sports drinks to replenish electrolytes.

It is possible, however, to drink too much water. Athletes are particularly at risk since they tend to drink large amounts of water or sports drinks to ward off dehydration. The excess fluid in your body can create dangerously low sodium levels. This condition, called hyponatremia, can cause seizures, confusion or even coma.

Again, there are certain health conditions that will require you to drink more water. If you frequently feel thirsty, despite drinking what should be an adequate amount of water, consult your doctor.

Do you have tips on staying hydrated? Please share them in the comments.

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